rofunc.utils.robolab.formatter.mjcf_parser.base

Base class for all MJCF elements in the object model.

1.  Module Contents

1.1.  Classes

Element

Abstract base class for an MJCF element.

1.2.  API

class rofunc.utils.robolab.formatter.mjcf_parser.base.Element

Abstract base class for an MJCF element.

This class is provided so that isinstance(foo, Element) is True for all Element-like objects. We do not implement the actual element here because the actual object returned from traversing the object hierarchy is a weakproxy-like proxy to an actual element. This is because we do not allow orphaned non-root elements, so when a particular element is removed from the tree, all references held automatically become invalid.

abstract get_init_stack()

Gets the stack trace where this element was first initialized.

abstract get_last_modified_stacks_for_all_attributes()

Gets a dict of stack traces where each attribute was last modified.

abstract is_same_as(other)

Checks whether another element is semantically equivalent to this one.

Two elements are considered equivalent if they have the same specification (i.e. same tag appearing in the same context), the same attribute values, and all of their children are equivalent. The ordering of non-repeated children is not important for this comparison, while the ordering of repeated children are important only amongst the same type* of children. In other words, for two bodies to be considered equivalent, their child sites must appear in the same order, and their child geoms must appear in the same order, but permutations between sites and geoms are disregarded. (The only exception is in tendon definition, where strict ordering of all children is necessary for equivalence.)

*Note that the notion of “same type” in this function is very loose: for example different actuator element subtypes are treated as separate types when children ordering is considered. Therefore, two <actuator> elements might be considered equivalent even though they result in different orderings of mjData.ctrl when compiled. As it stands, this function is designed primarily as a testing aid and should not be used to guarantee that models are actually identical.

Args:

other: An mjcf.Element

Returns:

True if other element is semantically equivalent to this one.

abstract property tag

abstract property spec

abstract property parent

abstract property namescope

abstract property root

abstract prefixed_identifier(prefix_root)

abstract property full_identifier

Fully-qualified identifier used for this element in the generated XML.

abstract find(namespace, identifier)

Finds an element with a particular identifier.

This function allows the direct access to an arbitrarily deeply nested child element by name, without the need to manually traverse through the object tree. The namespace argument specifies the kind of element to find. In most cases, this corresponds to the element’s XML tag name. However, if an element has multiple specialized tags, then the namespace corresponds to the tag name of the most general element of that kind. For example, namespace=’joint’ would search for <joint> and <freejoint>, while namespace=’actuator’ would search for <general>, <motor>, <position>, <velocity>, and <cylinder>.

Args:

namespace: A string specifying the namespace being searched. See the

docstring above for explanation.

identifier: The identifier string of the desired element.

Returns:

An mjcf.Element object, or None if an element with the specified identifier is not found.

Raises:

ValueError: if either namespace or identifier is not a string, or if

namespace is not a valid namespace.

abstract find_all(namespace, immediate_children_only=False, exclude_attachments=False)

Finds all elements of a particular kind.

The namespace argument specifies the kind of element to find. In most cases, this corresponds to the element’s XML tag name. However, if an element has multiple specialized tags, then the namespace corresponds to the tag name of the most general element of that kind. For example, namespace=’joint’ would search for <joint> and <freejoint>, while namespace=’actuator’ would search for <general>, <motor>, <position>, <velocity>, and <cylinder>.

Args:

namespace: A string specifying the namespace being searched. See the

docstring above for explanation.

immediate_children_only: (optional) A boolean, if True then only

the immediate children of this element are returned.

exclude_attachments: (optional) A boolean, if True then elements

belonging to attached models are excluded.

Returns:

A list of mjcf.Element.

Raises:

ValueError: if namespace is not a valid namespace.

abstract enter_scope(scope_identifier)

Finds the root element of the given scope and returns it.

This function allows the access to a nested scope that is a child of this element. The scope_identifier argument specifies the path to the child scope element.

Args:

scope_identifier: The path of the desired scope element.

Returns:

An mjcf.Element object, or None if a scope element with the specified path is not found.

abstract get_attribute_xml_string(attribute_name, prefix_root=None)

abstract get_attributes()

abstract set_attributes(**kwargs)

abstract get_children(element_name)

abstract add(element_name, **kwargs)

Add a new child element to this element.

Args:

element_name: The tag of the element to add. **kwargs: Attributes of the new element being created.

Raises:

ValueError: If the ‘element_name’ is not a valid child, or if an invalid

attribute is specified in kwargs.

Returns:

An mjcf.Element corresponding to the newly created child element.

abstract remove(affect_attachments=False)

Removes this element from the model.

abstract property is_removed

abstract all_children()

abstract to_xml(prefix_root=None, debug_context=None, *, precision=constants.XML_DEFAULT_PRECISION, zero_threshold=0)

Generates an etree._Element corresponding to this MJCF element.

Args:

prefix_root: (optional) A NameScope object to be treated as root

for the purpose of calculating the prefix. If None then no prefix is included.

debug_context: (optional) A debugging.DebugContext object to which

the debugging information associated with the generated XML is written. This is intended for internal use within PyMJCF; users should never need manually pass this argument.

precision: (optional) Number of digits to output for floating point

quantities.

zero_threshold: (optional) When outputting XML, floating point quantities

whose absolute value falls below this threshold will be treated as zero.

Returns:

An etree._Element object.

abstract to_xml_string(prefix_root=None, self_only=False, pretty_print=True, debug_context=None, *, precision=constants.XML_DEFAULT_PRECISION, zero_threshold=0)

Generates an XML string corresponding to this MJCF element.

Args:

prefix_root: (optional) A NameScope object to be treated as root

for the purpose of calculating the prefix. If None then no prefix is included.

self_only: (optional) A boolean, whether to generate an XML corresponding

only to this element without any children.

pretty_print: (optional) A boolean, whether to the XML string should be

properly indented.

debug_context: (optional) A debugging.DebugContext object to which

the debugging information associated with the generated XML is written. This is intended for internal use within PyMJCF; users should never need manually pass this argument.

precision: (optional) Number of digits to output for floating point

quantities.

zero_threshold: (optional) When outputting XML, floating point quantities

whose absolute value falls below this threshold will be treated as zero.

Returns:

A string.

abstract resolve_references()